After reading the book, I was so excited to see the film, especially knowing Gene Hackman played Sam. The problem is that the book did such an amazing job with slow cooking such an amazing story full of complexities, thrills, and emotion over almost 1000 pages. This kind of masterpiece is impossible to recreate in a two-hour movie. Because of this fact, the movie completely butchered the book, and the plots are almost unrecognizable. I think the only thing that both agreed on was the bombing in the beginning.
Another issue I had with the film was that it missed obvious details that came from the book but didn't change it for the film. For example, without spoiling anything too important, when Adam is speaking with Ruth Kramer, she says that her boys would be the same age as Adam is now had they not died. Since the movie switched the timelines around from the book, the boys would actually be almost 40 where Adam is only 26. Those little things kind of gnawed at me during the film while trying to adjust to the massive plot changes.
I don't regret seeing it because it reinforces the old adage that the books are almost always better than their movies.